Two technologists living in Switzerland, Baldur Eliasson and Ulf Bossel, believe that a methanol economy might be a better option than a hydrogen one and have placed a paper called 'The Future of the Hydrogen Economy: Bright or Bleak?' on the web drawing attention to some of the problems with hydrogen. The paper seems to have caused many people to doubt whether hydrogen is the solution they had believed it to be, which is why we are discussing it here. Its main conclusions are:

1. PIPELINE LOSSES

Hydrogen should not be pumped for long distances through pipelines because of the amount of energy lost in doing so. Most gas pipelines power the pumps along their length by burning some of the gas they are pumping. With natural gas, which is mostly methane, these pumps take 0.2% of the gas in transit every 100 km. However, because hydrogen is a less-dense gas than methane, a lot more of it must be moved to transport the same amount of energy. Either bigger pipelines must be built, which takes a bigger energy investment, or the gas has to move faster, causing energy losses from the increased turbulence. Eliasson and Bossel (E&B) estimate that about 0.8% of the gas would be lost per 100km and that, if solar energy was used in North Africa to produce hydrogen to send to industrial Europe, only 60-70% would actually arrive.

"Such long distance transport wouldn't be done with compressed gas" Werner Zittel comments. "Why transport electrolytically-produced hydrogen instead of transporting the electricity and converting it to hydrogen at the consumption site? The more decentralised your energy production chain, the shorter the average transport distances for hydrogen." Zittel also says that the E&B loss figures are roughly twice those calculated by his company.

2. DELIVERY PROBLEMS

The low energy density of hydrogen means that a lot more road tankers are going to be needed to get it to filling stations if it goes in compressed rather than liquid form. E&B compare 40-ton trucks, one carry hydrogen at 200 bar, another methane at the same pressure, and others carrying methanol, propane and ordinary petrol. "At 200 bar, the 40-ton truck can deliver about 3.2 tons of methane" they write, "but only 320Kg of hydrogen." As a result, it would take two methane deliveries and 21 hydrogen deliveries to supply the same amount of energy as carried by the petrol tanker. The wish to avoid this problem may be the reason that GM and BMW have chosen to use liquid hydrogen in their cars. (See page 134) Here again, Zittel disputes the E&B estimates. "If liquid hydrogen is transported in a 40 ton truck, about 3,500 kg can be delivered." he says.

3. COMPRESSION COSTS

E&B say that using electricity to make and compress hydrogen at a filling station would involve the loss of over 40% of the energy in the electricity. Zittel responds that it is wrong just to look at this single step and calculate its efficiency. "What has to be done is to look to the whole "well-to-wheel" chain and compare efficiencies of various alternatives over the full chain, not each individual step" he says. "Remember a hydrogen fuel cell is twice as efficient as an internal combustion engine. My firm has carried out analyses of various whole chains for many years for several ministries in Germany, for car companies and for the oil industry (CONCAWE) which did not even favour the hydrogen path. We have analysed about 200 various paths. Our results and assumptions have been crosschecked and discussed by both car companies and oil firms. We are therefore pretty confident that the hydrogen route is best."

In view of these and other problems they claim to have quantified, E&B suggest that a methanol (methyl alcohol, CH3OH) economy might be a better option than a hydrogen one because methanol is a liquid at normal temperatures and can thus be pumped and stored much more easily. It can also be burned in fuel cells. They write:

The synthesis of methanol requires hydrogen and carbon atoms. In a future sustainable energy world carbon could come from plant biomass, from organic waste and from captured CO2. Typically, biomass has a hydrogen-to-carbon ratio of two. In the methanol synthesis two additional hydrogen atoms could be attached to every biomass carbon. Carbon from the biosphere may become the key element for in a sustainable energy future. Instead of converting biomass into hydrogen, hydrogen from renewable sources should be added to biomass to form methanol. Carbon atoms should stay bound in the energy chain as long as possible. They are returned to the atmosphere (or recycled) after the final use of energy. But synthetic methanol is one of a number of options to be seriously considered for the planning of a clean and sustainable energy future.

Again, Zittel disagrees. "Over the full well-to-wheel path, methanol is less efficient than hydrogen. Secondly, the direct methanol fuel cell is less efficient and has a shorter life than a hydrogen fuel cell. Thirdly, methanol needs special safety measures to be taken, mainly in repair workshops. According to BMW, it is impossible to ensure these measures are applied in all workshops. This makes it impossible for methanol cars to be repaired around the world without severe safety risks for the repair staff. According to BMW this drawback eliminates methanol from consideration as a motor fuel regardless of any other technical arguments. Finally, my company does not know of any car company that is still considering methanol as vehicle fuel".

The safety aspects that worried BMW arise because methanol is extremely poisonous - less that a cupful can lead to permanent blindness or death - and it doesn't have to be swallowed to be dangerous since the liquid can be absorbed through the skin and the vapour through the lungs. Chronic inhalation or oral exposure may result in headache, dizziness, giddiness, insomnia, nausea, gastric disturbances, conjunctivitis, blurred vision, and blindness. No information is available on the reproductive, developmental, or carcinogenic effects of methanol in humans but birth defects have been observed in the offspring of rats and mice exposed to methanol by inhalation. The United States' Environmental Protection Agency has not classified methanol as carcinogenic.

Another problem is that methanol vapour is heavier than air and, unless there is good ventilation, it will linger close to the ground or in a maintenance pit where the mixture of vapour and air is liable to be set alight by a spark if the concentration of methanol is above 6.7%. and will explode if the temperature is above 12 C. Once ablaze, the flames give out very little light making it very hard to see them or even estimate the size of the fire, especially in broad daylight. Fortunately, methanol vapour has a repulsive, pungent odour so it gives some warning of its presence. However, it is difficult to smell methanol in the air at less than 2,000 parts per million.

Zittel's company plans to publish a detailed response to E&B in mid-2003. "[E&B] sketch spurious scenarios and the results are horrible," he says, "but if you use quite different scenarios they will give you completely different results. [They] take part of today's hydrogen technology and extrapolate it into the future. This is at the same level as people who argue that photovoltaics will never come because today's solar electricity costs about 0.5 Euro per kWh. They ignore the possibility of lower costs from greater economies of scale and longer learning curves. For instance, they calculate the electricity consumption for liquefaction of about 35 %. However, state-of-the-art concepts indicate that this consumption can be reduced close to 20 % when the next generation of liquefiers is built."

Despite the problems, the methanol economy is an option that Ireland should certainly consider, not as an alternative to the hydrogen economy but as a supplement to it. Methanol would allow hydrogen from surplus wind-generated electricity to be combined with biomass grown on farms and the resulting fuel sold throughout Europe. Moreover, the investment required to develop a network of methanol filling stations would be very much less than for its hydrogen equivalent.

SOURCES